Folliculogenesis is a precise series of developmental events that requires the co-operative efforts of several cell types comprising the Graafian follicle and the integration and modulation of a complex set of chemical messages that ultimately insure maturation and survival of the oocyte and finally brings about its ovulation. Basic to any attempt to elucidate the integrated functions of the developing Graafian follicle resides in the understanding of the unique structural and physiological features of each compartment. A defect in one cell type or one compartment may have marked repercussion on another compartment. This is particularly true during the atretic process or during the formation of a polycystic ovary (PCO) which we have called attenuated atresia. The objective of this proposal is to learn some of the basic, fundamental aspects of the dynamic morphology and function of the multifunctional granulosa cell as it is related to follicular development under normal and experimental conditions. THE SPECIFIC AIMS OF THIS PROPOSAL ARE (A) THE DETERMINATION OF THE STRUCTURE AND FUNCTION OF THE BASEMENT MEMBRANE OF THE DIFFERENTIATING FOLLICLE, (B) THE DEFINITION OF THE CYTOSKELETON OF GRANULOSA CELLS AT DIFFERENT PHASES OF FOLLICULAR DEVELOPMENT IN VIVO AND CHANGES IN RESPONSE TO STEROID HORMONES AND GONADOTROPINS IN VIVO AND IN VITRO, (C) THE CHARACTERIZATION OF ENDOCYTOSIS FOLLOWING RECEPTOR-LIGAND INTERACTION OF THE LIPOPROTEIN AND GONADOTROPINS IN DIFFERENT PHASES OF FOLLICULAR DEVELOPMENT "IN SITU", (D) THE CHARACTERIZATION OF GRANULOSA CELLS' RESPONSE (IN VITRO) WITH AND WITHOUT THE PRESENCE OF THECA AND WITH THECAL PIECES REPLACED TO DEFINE THE INFLUENCE OF THECAL ELEMENTS AND EXTRACELLULAR MATRIX ON GRANULOSA CELL STRUCTURE AND FUNCTION AND (E) THE EXAMINATION OF THE OOCYTE-GRANULOSA CELL INTERACTION (UNCOUPLING EFFECT) IN RESPONSE TO DIFFERENT HORMONES IN AN ATTEMPT TO MIMIC "ATRESIA." THE PROPOSED EXPERIMENTS WILL USE IN VIVO AND IN VITRO TECHNIQUES, (ORGANOTYPIC AND CELL CULTURE), LIGHT AND ELECTRON MICROSCOPY, FREEZE FRACTURE, IMMUNOCYTOCHEMICAL METHODS, CYTOCHEMISTRY, RADIOIMMUNOASSAY, COLLOIDAL GOLD-PROTEIN A IMMUNOCYTOCHEMICAL METHODS AND ELECTROPHYSIOLOGICAL TECHNOLOGY. The expected fundamental data will be integrated with that obtained about the reproductive process in general through other biological disciplines.